A circuit for generating and detecting ultrasonic sensing signals is provided. A piezoelectric device having a transmitting electrode and a receiving electrode is coupled to a biasing-and-sampling sub-circuit configured to set different bias voltages to the receiving electrode. The piezoelectric device is configured to transmit an ultrasonic signal upon applying an exciting pulse signal to the transmitting electrode and alternatively to generate a voltage signal at the receiving electrode upon receiving an echo signal based on the ultrasonic signal. A signal-collecting sub-circuit is coupled to the receiving electrode to determine a first sampling voltage based on the voltage signal at the receiving electrode in a first sampling period and a second sampling voltage based on the voltage signal at the receiving electrode in a second sampling period. An output sub-circuit is coupled to the signal-collecting sub-circuit for outputting the first sampling voltage and the second sampling voltage at a same time.